Cooperative Institute for Research in Environmental Sciences

McMurdo Project: Lidar Refurbishment, Upgrade & Sky Test at Boulder

Before we deployed the lidar to the McMurdo Station, mid-way between the South Pole and Antarctic Circle, we must first refurbish and upgrade the Fe Boltzmann temperature lidar at the University of Colorado to restore and enhance its specifications.

This alexandrite-laser-based Fe Boltzmann lidar was originally developed at the University of Illinois in 1997 by Dr. Chu and Dr. Gardner in collaboration with their colleagues. This lidar is a solid-state dual-channel resonance-fluorescence lidar. The lidar contains two laser transmitters and two optical receivers. Each transmitter consists of an injection-seeded, frequency-doubled, flashlamp-pumped, alexandrite laser. The injection seeders are tunable external cavity diode lasers. Wavelength control of the seeders is accomplished via an accurate wavelength meter. Each receiver consists of a 40-cm Schmidt–Cassegrain telescope with enhanced UV dielectric coating. The return signal is collimated, passed through an interference filter, and then detected by a photon counting PMT. For daytime operation, a pressure-tuned, temperature-stabilized Fabry-Perot etalon is employed in each receiver to reject the solar background. The design, development, and performance of this lidar can be found in Chu et al. [Applied Optics, 2002].

Since its first airborne deployment to Okinawa in November 1998 during the Leonid meteor shower campaign, the Fe Boltzmann lidar has been deployed to the North Pole and the Arctic aboard the NSF/NCAR Electra aircraft, to the Amundsen-Scott South Pole Station, and to Rothera, Antarctica. Significant scientific discoveries have emerged from these observations (see "Results from prior campaigns").

After nearly a decade deployment under harsh conditions, refurbishment of the system hardware and software was necessary in order to restore its operation to the original specifications. More importantly, new technologies have emerged in the last five years that provide better control of alexandrite laser spectrum and power, and more stable seed lasers with higher power. Incorporation of these new technologies into the existing lidar system will significantly improve its performance and enhance its ability to address the proposed polar science.

The happy crew (from left: Zhangjun Wang, Weichun Fong, Wentao Huang, and Xinzhao Chu) with the upgraded lidar transmitter. Wentao’s smile was magnificent, as his hard work of refurbishing and upgrading two alexandrite lasers was finally paid off when the lidar worked properly and happily took good Fe data again.